class_docstr: Simple stage that stacks GNN layers.
code: def __init__(self, dim_in, dim_out, num_layers):
      super().__init__()
      for i in range(num_layers):
          d_in = dim_in if i == 0 else dim_out
          layer = GNNLayer(d_in, dim_out)
          self.add_module(f"layer{i}", layer)
      self.dim_out = dim_out
  
file_path: pytorch_geometric/graphgym/custom_graphgym/stage/example.py
imports: import torch.nn
  import torch.nn.functional
  from torch_geometric.graphgym.config import cfg
  from torch_geometric.graphgym.models.layer import GeneralLayer
  from torch_geometric.graphgym.register import register_stage
label_desc: Use image node_id 1 to create a new GNNStackStage object from inherited base classes: nn with example: obj = GNNStackStage(dim_in, dim_out, num_layers)